This invention relates to an enhanced, high frequency, electrical data connector that includes a shorting system support integrally molded to the connector housing, where such system offers significantly reduced insertion loss for electrical signals communicated through the connector through decreased capacitive coupling and decreased mutual inductance between conductors, and lowered skin resistance and self inductance of the conductors.
Insertion loss, or attenuation, defined as the inductive and capacitive coupling from an active line or lines into another, causes degradation of signals, has been recognized for years and represented a performance limitation to increased data communication rates. Only recently, performance standards were established by the Telecommunications Industry Association (TIA) in cooperation with the Electronic Industries Association (EIA) for STP, or shielded twisted pairs of conductors. Specifically, the EIA/TIA established performance standards for various categories of products operating at frequencies up to 300 MHz, where STP-A products have the highest performance standards.
STP-A products, where the transmission requirements of such products are characterized up to 300 MHz, are typically intended for emerging applications with transmission rates up to 300 Mbps, or higher through encoding or wave reshaping. The standard is preliminarily identified as SP-2840, May 1993. While the invention hereof relates to the hardware or connector, it is important to note that the hardware is only one major component of a communication system. The other major component is the transmission cable. Thus, it is important to insure the use of the correct connecting component or hardware that is compatible with the transmission characteristics of the cable. Such cables may typically be high performance unshielded twisted-pair (STP) cables, the performance characteristics of which are covered by EIA/TIA bulletin SP-2840, which when adopted will be titled, "EIA/TIA-568, Commercial Building Telecommunications Wiring Standard."
Insertion loss, or attenuation, for the connectors is defined as a measure of signal power loss due to the connecting hardware and is derived from swept frequency voltage measurements on short lengths of 150 ohm shielded pair test leads before and after splicing-in the connectors under test. The worst case insertion loss, after cable calibration, STP-A connecting hardware is listed below in TABLE I.
TABLE I ______________________________________ 150 ohm STP-A Connecting Hardware Maximum Insertion Loss Limits As Specified In EIA/TIA Document SP2840/568 For Prime And Self-Shorting Paths Frequency Maximum (dB) ______________________________________ 100.0 KMHz .05 4.0 MHz .05 8.0 .10 10.0 .10 16.0 .15 31.25 .15 62.50 .20 100.0 .25 300.0 .45 ______________________________________
Insertion loss performance standards have now been extended to include STP, or shielded twisted pairs of conductors, at frequencies greater than 100 MHz under EIA/TIA SP2840-568, where such standards exceed Category 5 for UTP with signal frequencies up to 300 MHz.
The present invention represents an enhancement to the shielded data connector disclosed and claimed in copending application U.S. Ser. No. 08/101,529, filed Aug. 3, 1993, assigned to the Assignee hereof, where the disclosure of such copending application is incorporated herein by reference.
The use of shielded electrical connectors, generally, is well-known. Certain types of applications, such as computer systems, require connectors which will both reliably establish an electrical connection and provide shielding for the data signal conductors. In many applications, this shielding is coupled to the shield braid of a shielded cable. Typically, the cables utilize shielded twisted pair conductors to minimize signal cross-talk within the cable.
Conventional shielded electrical connectors provide for shielding around the connector, to minimize adverse interference from outside to the connector to signals being conducted within the connector. Such connectors have been widely used. Conventional connectors, however, do not address the possibility of signal cross-talk or insertion loss proximate the termination of each conductor, where the twisted pairs are no longer intertwined. Accordingly, while conventional connectors guard against signal interference from outside the connector, they do not include provisions for controlling cross-talk or insertion loss between signal conductors inside the connector.
In the copending application reduced insertion loss is achieved by means within the hardware, i.e. connector. In one embodiment thereof, a shield member extends between the conductors of two different twisted pairs as they extend beyond the cable shield. In one preferred embodiment, the shield assembly also includes conductive surfaces which extend around at least a portion of the contact assembly i.e., between the contact assembly and at least portions of the upper, lower, and side surfaces of the connector housing. Also in this preferred embodiment, contact portions of each of the electrical contacts will extend in generally parallel relation to one another, but contact portions of contacts coupled to conductors of different signals are spaced from one another by an air gap along at least a portion of their parallel-extending length.
Improved insertion loss performance for the connector herein, particularly a 4-position data connector, is achieved by the inclusion therein of an integral shorting assembly which utilizes a pair of formed, U-shaped, circular conductors having a non oxidizing surface where which the respective ends of the legs are reversely bent, while providing closed loop shorting.
The use of a shunt or shorting assembly in electrical connectors has been known to ensure electrical continuity during periods of unmating, for example, or provide rerouting of signals during periods of unmating for selected conductors within the connector, i.e. a token ring system.
U.S. Pat. No. 4,449,778 discloses as a preferred embodiment thereof a shielded 4-position data connector which uses a pair of identical, stamped shunting bars, where the shunting bars are spaced-apart and parallelly arranged in aligned slots in the connector housing and oriented with different pairs of the four terminals in the connector to provide shunting between the terminals of a given pair.
U.S. Pat. No. 4,682,836 is directed principly to a latching mechanism for a pair of matable electrical data connectors. However, in the construction of the connectors, the patent discloses the use of a discrete insertable member or block into which a pair of staggered slots have been provided to receive complementary shunting elements formed of metal wire, each shaped as a channel with laterally extending feet. Typically, such channel shaped shunting elements are bottom loaded into the slots of the block, with the feet exposed to contact a pair of terminals within the connector, whereupon the block is inserted into a shunting position in the connector housing.
The present invention provides an effective system for providing a closed loop arrangement through shunting or shorting, while offering superior reduced cross-talk performance and insertion loss in a shielded electrical data connector. These and other features will become apparent in the description which follows, particularly when read in conjunction with the accompanying drawings.